Hollow ball and process of making the same



Dec. 22, 1925. 1,566,974

1 A. T. SAUNDERS HOLLOW BALL AND PROCESS OF MAKING THE SAME Filed May 8, 1923 I Inventor.

Addisofi I? Saunders", zjmg w Patented D... 22, 1925.

UNITED STATES ADDISON '1. SAUNDERS, OF AKRON, OHIO,

PATENT OFFICE.

ASSIGIN OR TO A. G. SPALDING :9: BROS, OF

NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

HOLLOW BALL AND PROCESS OF MAKING THE SAME.

Application filed May a,

.1 and Processes of Makin the Same, of which the following is a speci cation.

Certain features of the invention are illustrated in the accompanying drawing in which- Figure 1 shows a hemispherical section or blank for one half the ball and a mass of material for coating the same.

, Fig. 2 illustrates a pair of hemispherical blanks with the air proof coating applied, and with a seam sealing bead in its initial state and position ready to be subjected to a vulcanizing heat for forming a union at the meeting edges of the blanks.

Fig. 3 is a detail sectional view s owing the'seam after the members shown in Fig. 2 have been subjected to the vulcanizing heat and the seam sealed.

This invention is designed primarily as an improvement in tennis balls and other hollow playing balls having a charge of compressed air (or gas) such as balls for the games of squash," handball, racquets, etc., and in the process of manufacture of the same. The principal objects are to accomplish,

' by preventing leaking of the air charge, the maintenance, through a protracted period of a uniform degree of resiliency in such balls and to secure the desired degree of firmness of feeling without excessive air charge. 'One of the chief weaknesses in balls of this class is their inability to retain the air charge through a protracted period. There is a continual reduction in their resihency, because of leaking, from the moment of 1nflation.

To obtain thedesired action in this class of balls the thickness to which the wall of rubber or rubber compound can becarried is limited, and to such degree that with the usual character of compounds vfor such walls,

whichmust be used to meet the requirea inents, they have a considerable porosity,

' thus permitting the escape of the air charge.

, Accompanying this loss of resiliency v through a'lessened air charge, the playing qualities are impaired in another way:

1923. Serial No. 637,532.

When such balls are fully inflated, a comparatively small portion of the surface is depressed by the impacts incidental to play. When the balls are partially deflated, by a leaking of the air charge, a greater part Of the surface is depressed on impact with the racquet or other implement, or with the ground, resulting in a different degree of grip thereon, which, it will be understood,

demands a different stroke for a given result.

And'since in expert pla the character of the various strokes is esta lished upon the behavior of fresh, fully inflated balls, it will be seen that, owing to the varying degrees of inflation in which balls put upon the marketi reach the general player, great variations exist in-controllability and in the character of strokes required, which affect the accuracy and pleasure of play, often beyond the knowledge of the user.

I overcome these weaknesses by employing an airtight liningfor the hollow ball, which is also of a character to reenforce and support the wall and produce an increased firmness for a given total thickness, which firmness is now sometimes obtained by an undesirably high .initial air charge, resulting in over-resiliency while the ball is fresh.

This lining comprises a gelatinous material, glue or gelatin, with an admixture of a softening agent such as glycerine, or m0- lasses, and in such proportions as to be nonflowng under heat when the aqueous moisture, (water content), preferably incorporated to enable mixing and spreading, is eliminated. y

In the manufacture of hollow rubber balls, or centers as they are termed when they are employed in combination with a cover of another material, as in tennis balls, two general methods are employed. In one the rubber compound is prepared in sheets of the desired thickness for the wall, and from this sheet are out sections of a size and shape to form -a suitable hollow biscuit when a number arejoined up at their edges into a closed hollow unit. These are inflated to fit the vulcanizing mold either by enclosing. a material which generates a gas under the spherical sections are formed in molds and partially cured to cause them to retain their shape and these are brought together in a second mold and so sealed into a unitary hollow sphere and fully vulcanized; the air charge being introduced at the proper stage t sheeted sections, the rubber compound is in a raw state, and, in the case of the hollow, hemispherical sections, when they are in the semi-cured condition before they arejoined in the final curing mold.-

One of these hemispherical sections is shown at 1 in Figure 1, before the coating is applied. A working recipe for the lining compound is: strong, thin sheet glue or gelatine35 parts by weight, glycerine 25 parts by weight, water q. s.

The desirable quantity of water is that which will soak up in the glue in a period of from one half hour to three hours, at normal temperature, the time depending on the desired consistency for the particular use or method by which it is 'to be applied, and the thickness of the sheet glue employed.

To mix: Immerse the glue in clean cool water and while it is soaking ii at the glycerine in a suitable container, ha ing means for slow'stirring, to about 200 F. A waterjacketed kettle is best. When the glue has taken up sufiicicnt water (to be determined for any given coat by tests,) the surface water should be drained off, and while maintaining the temperature of the'glycerine, the soaked glue is gradually added, stirring gently. NVhen the mixture is complete and thorough, still maintain the heat until any air bubbles which have formed-have risen to the surface.

To use on, the sheeted stock the mixture may be drawn from a faucet (preferably near the bottom of the container) and applied while warm to the sheeted compound by flowing, smearing, or spreadingf The rubber sheet and the tools or appliances should also be kept warm to prevent the settirigof the coating of the gelatinous mixture.

.When the proportions of glueand glycerinef are approximately as given above, and 'tliewater not excessive, the coating will set as it cools. v So long as the water remains in the coat- 'ing',said coating will flow'again on reheating. The water is therefore to be driven or allowed to dry out. After a portion of the water. is out, the temperature may be gradually raised in driving off the rest (without disturbing the coating), thus hastening the'drying.

' When the water is out the remaining mix ture of glycerine and glue forms a pliable, elastic, airtight lining (or film) which will not flow under heat. It is, therefore, not displaced when the sheeted stock"is made up into centers or balls, and is not caused to flow or impaired by the heat of the usual vulcanization. The coating has the characteristic that it is flexible and extensible and thus accommodates itself to the action of the wall, to which it is applied, which in the case of tennis balls is of rubber.

The behavior of the mixture isthe same when applied to the'hollow hemispherical sections used in the second method described for making hollow balls. But owing to the fact that the inner surface of these sections (because of their shape) cannot be spread in the same way as for the sheet stock, the application is best made by painting or smearing the mixture in a flowing condition into the cavity, when the section is slightly warm. It then sets quickly and without requiring tumbling, or further attention more than merely reversing posit on once or twice to prevent unevenness.

Any unevenness which may occur from imperfect handling may be corrected while the water is still in the mixture by heating the section and manipulating it to cause the soft mixture to flow into an even layer.

I find that I can best lay this lining in the hollow sections by first molding the gelatinous mixture into cylindrical rods or daubersiof a diameter somewhat less than that of the cavity, in the section and with a rounded nose conforming to the cavity as at 2 Fig. 1.

When the gelatinous mixture is drawn ("from the mixer) into the cylindrical molds it sets on cooling and retains its form.

Care must be taken tokeep the water from drying out before. using, by keeping the daubers in a tight container or humidor until ready to use. In applying the lining, the sections should be slightly .warmedto a temperature of 100 to' 140 F.and in applying by hand, the operator heats the nose of the dauber for only an instant in a gas jet, melting only a thin outer layer of the compound; holding the dauber with ne hand and the section in the other, inserts the dauber nose into the cavity and with a combined and opposite twisting motion of the two wrists, smears the melted compound (or gelatinous mixture) evenly on the inner surface of the section. The coating thus applied is allowed to dry. 5

- As suggested, the sectionsmay be inverted once or twice during the short-time required for setting. The result of the described operation is a practically evenly distributed, non-flowing lining of the'gelatinous compound on the inner surface of the hemispherical section.

The convex. nose of the dauber is automatically kept in shape as it is used. When the piece grows too short to be conveniently held in the hand, another section of dauber having a flat end may be attached to the fiat end of the first, enabling the using of .all without waste or remolding. In making up the centers for vulcanizing, either from the fiat sheet stock or the sections which havebeen lined with the material, the edges which are to be joined must first be thoroughly freed from any of the gelatinous mixture, as its presence will prevent good seams.

' The making up of the centers or balls after the lining described above.

When the hollow ba ls, or centers, are made up of hemispherical hollow sections, as described in the second method above, a narrow line at the joint, or seam, may .remain without the airproof lining, owing to a slight overlapping of the beveled edges of the sections at A.

I remedy this by a second operation; laying an annular welt of a gelatindils mixture carrying a higher proportion of glycerine, in the section having the female bevel and just free of the edge of the bevel. The preponderance of glycerine causes the mixture to flow under the vulcanizing heat in spite of the absence of aqueous molsture.

The balls or biscuits are so'placed in the mold that this welt is above thet seam or joining place of the two halves, with the result that when the vulcanizing heat is applied for the final cure of the rubber, the

welt B is melted and flows into the angle,

formed by the projection inward of the male bevel, forming a seal covering the theretofore unlined projecting portion/of the male bevel.

To prevent any subsequent flowing of this softer mixture forming the seal, I combine with the glue and glycerine a small percent of albumen. This is coagulated by the heat of the cure and renders the mixture thereafter ,nonflowing.

' A mixture in suitable proportions for this seam-sealing compound 18 as'follows: Glue 50 parts by weight, glycerine 300 parts by weight, water by weight.

To mix, soak up the glue in cold clean water as forithe first mixture, mix with the glycerine, all as described above.

Dissolve the albumen in cold water enough tofirst well cover it in the dry condition.

Cool down the glue glycerine mixtureto below 140 F. to avoid coagulating the albu-' men and add the latter, stirring slowly till mixed. Then proceed to pour onto level glass slabs, or other suitable cooling'surfaces or trays, forming sheets. When 'tcold transfer the sheets to drying trays covered with non-sticking fabric. The sheets may be is applied has already beenq. s., dry egg. albumen 20 parts dried in a warming cupboard, gradually raising the temperature above normal as they become nearer dry, but never above 140 F.

After the sheets are dry the material is ready for use. I prefer to lay this welt of the seam, sealing mixture by spur-ting from a hand pressure device, having a suitable nozzle and electrically warmed to keep the material in a flowing condition.

What I claim is: v

1. A gas filled playing ball of the tennis type having its vulcanized rubber wall provided on its inner side with an adherent air proof layer of dehydrated non-coagulablc compound comprising gelatine and a softening material/in proportions to be non-fluent under heat and to give a greater firmness to said wall than would a like increase in the thickness of the rubber wall itself, substantially as described.

2. A gas filled playing ball ofthetennis type having its vulcanized rubber wall in sections, each of which is provided on its inner side with a dehydrated gelatinous layer non-fluent under heat adherent thereto before uniting with the other section, said layer adding support to the wall, substan- I tially as described.

3. A playing ball having its vulcanized rubber wall composed of two hemispherical members, each interiorly and individually coated with gelatinous material before joining with the other section, said coating adding support to the rubber wall.

4. A blank for making a hollow playing ball, consisting of a section of vulcanizable rubber having a coating of gelatinous material on that face which is to be the inner side of the completed ball,.said coating being air proof, non-fluent under vulcanlzlng heat, resilient, andadding support-to the rubber wall.

5. A blank in accordance with claim 4 for making a hollow playing ball, in which the gelatinous coating contains glycerine.

6. A blank for a hollow rubber ball comprising a section of rubber having a coating on that face which is to be inside the completed ball, said coating being of a mixture containing gelatinous material, said coating being freed from the water used in the mixture and thereby rendered non-flowing under heat, substantially as described.

7. Blanks for making a hollow playing ball, consisting of hollow hemispherical fluent under heat, then forming the hollow biscuit from said coated rubber with the coating inside, and vulcanizing.

9. The process according to claim 8 in which the gelatinous material is composed of gelatin and glycerine.

10.7 In a process of making gas filled hollow balls formed of sections united into a hollow member, the steps comprising laying adjacent the edges of the sections to be joined, a ring of gelatinous material adapted to flow under gentle-heat and to he rcn dered n'onflowing by a higher temperature, joining the sections into a hollow wall with the gelatinous material on the inside, applying aheat sufiicient to cause the gelatinous material to flow and seal the joint, and following with ahigher heat to render the gelatinous material non-flowing under subsequent heat.

In testimony'whereof. I afiix my signature.

ADDISON-T. SAUNDERS. 

